[Simh] Photorealistic panel for PDP-11/20

[Phil Budne]

When I did the PDP-7 "second seat" graphics "glass TTY" device driver
for UNIX-7 under SIMH, I put in comments musing about how a more
faithful user experience (*) could be created using websocket (or
"Comet" aka reverse AJAX) and JavaScript.

This could also be done for front panels (implemented as browser
screens). But I didn't get encouraging feedback about the idea!

(*) The screen fills up from top to bottom, and when all the screen
lines have been used, or when the command list buffer is full, a
button is lit, and you have to press on the button to clear the screen
and continue.